RF transmitter, integrated circuit device, wireless communication unit and method therefor

Abstract

A radio frequency (RF) transmitter has at least one digital signal processing module and at least one power amplifier module. The digital signal processing module includes at least one digital pre-distortion component arranged to receive at least one complex input signal, perform two-dimensional non-uniform mapping of the complex input signal to a first, in-phase, digital pre-distortion control word and a further, quadrature, digital pre-distortion control word, and output the in-phase and quadrature pre-distortion digital control words. The power amplifier module includes a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells. The two-dimensional non-uniform mapping has a pre-distortion profile at least partly based on an input/output relationship for the power amplifier module arranged to generate an analog RF signal based at least partly on the in-phase and quadrature digital pre-distortion control words.

What is claimed is: 
     
       1. A radio frequency (RF) transmitter comprising:
 at least one digital signal processing module comprising:
 at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to:
 receive at least one complex input signal, 
 receive at least one feedback signal from the at least one digital pre-distortion component, 
 apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and 
 output at least one noise shaped complex input signal; and 
 
 
 
       wherein the at least one digital pre-distortion component is arranged to:
 receive the at least one noise-shaped complex input signal comprising information to be transmitted over an RF interface, 
 perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital pre-distortion control word and a further, quadrature digital pre-distortion control word, and 
 output the in-phase and quadrature digital pre-distortion control words; and 
 at least one power amplifier module comprising a digital power amplifier (DPA) having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells, wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one noise-shaped complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to:
 receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, and 
 generate the analog RF signal for transmission over the RF interface based at least partly on the in-phase and quadrature digital pre-distortion control words. 
 
 
     
     
       2. The RF transmitter of  claim 1  wherein the at least one digital pre-distortion component is arranged to:
 identify a closest matching predefined vector for the received noise-shaped complex input signal within the pre-distortion profile; and 
 map the identified closest matching predefined vector to a set of digital control words to be output. 
 
     
     
       3. The RF transmitter of  claim 1  wherein the at least one noise shaping component and the at least one digital pre-distortion component form at least part of a delta sigma modulator. 
     
     
       4. The RF transmitter of  claim 1  wherein the at least one digital signal processing module comprises an up-sampling component arranged to perform up-sampling of the received at least one complex input signal thereby increasing a sample rate of the received at least one complex input signal to an input data rate of the DPA. 
     
     
       5. The RF transmitter of  claim 1  wherein:
 the first array of switch-mode power cells is arranged to receive at least a part of the first, in-phase digital control word and to generate a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and 
 the at least one further array of switch-mode power cells is arranged to receive the at least one further, quadrature, digital control word and to generate at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word. 
 
     
     
       6. The RF transmitter of  claim 5  wherein the first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells are further arranged to receive respective carrier frequency signals, and to generate the respective in-phase and quadrature components of the analog RF signal further based at least partly on the received carrier frequency signals. 
     
     
       7. The RF transmitter of  claim 6  wherein the at least one power amplifier module comprises
 a first, in-phase, phase selector arranged to receive a carrier frequency signal and a first, in-phase, sign signal, and to output a first, in-phase, carrier frequency signal for the first, in-phase, array of switch-mode power cells; and 
 at least one further, quadrature, phase selector arranged to receive the carrier frequency signal and at least one further, quadrature, sign signal, and to output at least one further, quadrature, carrier frequency signal for the at least one further, quadrature, array of switch-mode power cells. 
 
     
     
       8. The RF transmitter of  claim 1  wherein the at least one power amplifier module comprises a magnitude and sign generator module arranged to:
 directly receive the digital pre-distortion control words output by the digital signal processing module; and 
 generate from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word. 
 
     
     
       9. The RF transmitter of  claim 1  wherein each array of switch-mode power cells comprises a plurality of inverse Class D structure switch-mode power cells. 
     
     
       10. An integrated circuit device comprising:
 at least one digital signal processing module comprising:
 at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to: 
 receive at least one complex input signal, 
 receive at least one feedback signal from the at least one digital pre-distortion component, 
 apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and 
 output at least one noise-shaped complex input signal; and 
 
 
       wherein the at least one digital pre-distortion component is arranged to:
 receive at least one noise-shaped complex input signal comprising information to be transmitted over a radio frequency (RF) interface, 
 perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital pre-distortion control word and at least one further, quadrature digital pre-distortion control word, and 
 an output port arranged to output the in-phase and quadrature digital pre-distortion control words to at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells, wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprising a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, 
 
       such that a combined output of the switch-mode power cells produces the analog RF signal for transmission based at least partly on the in-phase and quadrature digital pre-distortion control words. 
     
     
       11. The integrated circuit device of  claim 10  wherein the at least one digital pre-distortion component is arranged to:
 identify a closest matching predefined vector for the received noise-shaped complex input signal within the pre-distortion profile; and 
 map the identified closest matching predefined vector to a set of digital control words to be output. 
 
     
     
       12. The integrated circuit device of  claim 10  wherein:
 the first array of switch-mode power cells is arranged to receive at least a part of the first, in-phase digital control word and to generate a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and 
 the at least one further array of switch-mode power cells is arranged to receive the at least one further, quadrature, digital control word and to generate at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word. 
 
     
     
       13. The integrated circuit device of  claim 10  wherein the at least one power amplifier module comprises a magnitude and sign generator module arranged to:
 directly receive the digital pre-distortion control words output by the digital signal processing module; and 
 generate from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word. 
 
     
     
       14. A wireless communication unit comprising a radio frequency (RF) transmitter comprising:
 at least one digital signal processing module comprising: 
 at least one digital signal processing module comprising:
 at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to:
 receive at least one complex input signal, 
 receive at least one feedback signal from the at least one digital pre-distortion component, 
 apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and 
 output at least one noise shaped complex input signal; and 
 
 
 
       wherein the at least one digital pre-distortion component is arranged to:
 receive the at least one noise-shaped complex input signal comprising information to be transmitted over an RF interface, 
 perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital control pre-distortion word and a further quadrature digital pre-distortion control word, and 
 output the in-phase and quadrature digital pre-distortion control words; and 
 at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells, 
 
       wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to:
 receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, 
 such that a combined output of the switch-mode power cells produces the analog RF signal for transmission over the RF interface based at least partly on the in-phase and quadrature digital pre-distortion control words. 
 
     
     
       15. A method of generating a radio frequency signal for transmission over a radio frequency (RF) interface, the method comprising:
 receiving at least one complex input signal comprising information to be transmitted over the RF interface; 
 receiving at least one feedback signal from at least one digital pre-distortion component; 
 applying noise shaping to the at least one complex input signal based at least partly on the at least one feedback signal; and 
 outputting at least one noise-shaped complex input signal; 
 performing two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase, digital pre-distortion control word and at least one further, quadrature, digital pre-distortion control word; 
 providing the in-phase and quadrature digital pre-distortion control words to at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells; 
 
       wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells;
 receiving the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, and 
 combining an output of the switch-mode power cells; 
 producing the analog RF signal for transmission over the RF interface from the combined output of the switch-mode power cells based at least partly on the in-phase and quadrature digital pre-distortion control words. 
 
     
     
       16. The method of  claim 15  further comprising:
 identifying a closest matching predefined vector for the received complex input signal within the pre-distortion profile; and 
 mapping the identified closest matching predefined vector to a set of digital control words to be output. 
 
     
     
       17. The method of  claim 15  further comprising:
 performing up-sampling of the received at least one complex input signal thereby increasing a sample rate of the received at least one complex input signal to an input data rate of the at least one power amplifier module. 
 
     
     
       18. The method of  claim 15  wherein the step of generating an analog RF signal comprises:
 the first array of switch-mode power cells receiving at least a part of the first, in-phase digital control word and generating a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and 
 the at least one further array of switch-mode power cells receiving the at least one further, quadrature, digital control word and generating at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word. 
 
     
     
       19. The method of  claim 15  further comprising:
 directly receiving the digital pre-distortion control words; and 
 
       generating from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word.